This application relates to fiber devices with fibers engaged in grooves on substrates, and in particular, to fabrication of such fiber devices.
Optical fibers can be used to guide light from one location to another. A typical fiber may be simplified as a fiber core and a cladding layer surrounding the fiber core. The refractive index of the fiber core is higher than that of the fiber cladding to confine the light. Light rays that are coupled into the fiber core within a maximum angle with respect to the axis of the fiber core are totally reflected at the interface of the fiber core and the cladding. This total internal reflection provides a mechanism for spatially confining the optical energy of the light rays in one or more selected fiber modes to guide the optical energy along the fiber core. The guided optical energy in the fiber, however, is not completely confined within the core of the fiber. A portion of the optical energy can xe2x80x9cleakxe2x80x9d through the interface between the fiber core and the cladding via an evanescent field that essentially decays exponentially with the distance from the core-cladding interface. This evanescent leakage may be used to couple optical energy into or out of the fiber core, or alternatively, to perturb the guided optical energy in the fiber.
Fibers may be engaged to grooves on substrates such as V grooves in semiconductor substrates to form various fiber devices based on the evanescent leakage or coupling. A portion of the fiber cladding can be removed and polished to form a coupling window to allow for optical access to the fiber core via an evanescent field of a guided mode supported by the fiber.
This application includes fabrication techniques and related devices for simultaneously polishing fiber cladding of an array of fibers positioned in grooves of a substrate in a wafer-level fabrication process to achieve a high throughput. In one embodiment, a chemical mechanical planarization (CMP) technique is adopted to perform the polishing and to control the amount of removed fiber cladding. A special protection template may be provided to hold the substrate with an array of fibers in position and to protect the fibers from being damaged by the polishing pad and to improve the polishing uniformity. In addition, optical monitoring may be implemented to monitor the polishing in real time.